museum techniques in pathology.pptx

Pathology

1. Dr. Anju Shrestha PGY III, Pathology CMCTH MUSEUM TECHNIQUES

2. Introduction Pathological museums are in part historical, representing the pioneer work of diagnosticians and therapists. Presents records of past states, not now encountered, or conditions of great rarity. Provide the student with the basic material of his current teaching.

3. Basic museum techniques Reception Preparation Fixation Color restoration Preservation Mounting Special methods Presentation

4. Reception Museum specimens are collected from teaching hospitals. Necropsy specimens from postmortem room Research laboratories Specimen should be received with full details of the patient/lesion

5. Preparation of the specimen One of the commonest causes of inferior specimens is contact with tap water. The resultant haemolysis greatly reduces their value. Specimens should be washed only with saline, and should be kept in saline before demonstration. Drying ruins surface appearance. Should not be kept in saline for more than 2 hours as autolysis sets in.

6. Fixation of the specimen Objective: To preserve cells and tissue constituents in as close to life like state as possible Fixation stops autolysis and bacterial decomposition, and stabilizing the cellular and tissue constituents Fixatives are based on formalin fixative technique. They are derived from Kaiserling technique and its modification .

7. Kaiserling recommended that the initial fixation should be in neutral formalin (KI) solution and then preserving glycerine solution (KIII) for long term display. These solutions also preserve color.

8. Principle of fixation Specimens containing bile or stained by bile must be fixed and stored apart from others, as they will stain them. Specimens undergoing fixation must not touch other specimens, or the sides of jars; they must either lie on washed lint or be suspended by linen thread. Flat flaps of tissues like stomach, intestine etc. should be fixed to cork bread and left in formalin so that they are not crumpled and irregularly fixed. Cystic cavities- if unopened, should be injected with fixatives. Opened ones should be packed with cotton wool.

9. Solid viscera should be fixed by vascular injection. For eg , brain is fixed by injecting fixative through basilar artery. Lungs and limbs should be fixed by vascular injection.

10. Fixation technique Most widely used techniques are modification of methods described by Kaiserling (1897). Originally 3 solutions were used - First for fixing - Second for restoring color - Third as a mounting fluid

11. Kaiserling No. I- fixing fluid Formalin (40%) 400 ml. Pot. nitrate 30 g. Pot. acetate 60 g. Tap water 2,000 ml. Tissue is fixed in Kaiserling No.I solution for 24 hours to few weeks depending on the size of the specimen.

12. Kaiserling No. II solution The specimen is placed in 80% ethyl alcohol solution for an optimal period for 1 hour ( upto 4 hours depending on the size of specimen), if the specimen is discolored. If the specimen is left in alcohol for too long  the color will fade, and the effect is irreversible. This step is not required if mounting fluid used is sodium hydrogen sulfite.

13. Color restoration The fixed specimen is transferred to a jar containg industrial methylated spirit until the color is fully restored. The alcohol penetrates the tissue rapidly. Floating specimen  cover with surgical gauze. The vessel should be closed to prevent evaporation. Color restoration is complete in 2-8 hours, depending on the size and character of the specimen.

14. Restoration can be achieved by adding reducing agent- sodium hydrogen sulfite to the mounting fluid ( Pulvertaft , 1936). Specimen mounted show remarkably little fading even after 25 yrs.

15. Original Kaiserling No. III solution Glycerine 500 ml. Arsenious acid 1% 200 ml. Pot. acetate 250 g. Thymol 2.5 g .

16. Pulvertaft – Kaiserling mounting fluid III Glycerine 300 ml 10% sodium acetate 100 g 10% formalin 5 ml Tap water 1000 ml

17. Camphor/ thymol- prevents the growth of moulds . Immediately before sealing 0.4% sodium hydrosulfite is added. Solution should be filtered through paper pulp under negative pressure to remove impurities.

18. Carbon monoxide has also been employed as a colour -retaining agent. Schultz (1931) introduced the technique, which gives brilliant colour contrast, but entails the risks of poisoning and explosion. Pure liquid paraffin can be used as final mountant after color restoration with alcohol. It reduces discoloration of mounting fluid by pigments in the specimen.

19. Hollow viscera Cut hollow viscera should be padded with cotton wool. Uncut viscera can be pressure inflated. Eg - Through urethra into the bladder - Through urethra into pelvicalyceal system - Through trachea into the lungs - Direct injection in case of cysts The fixatives can be injected into such organs by Higginson syringe or with conventional hypodermic syringe .

20. Higginson syringe

21. Preservation The specimen together with a duplicate label, is wrapped in gauze or muslin and the label is attached with a piece of linen thread. Specimens are preserved in a rectangular earthenware tanks. The fluid used can be Kaiserling fixing fluid I for a period of six months. After 6 months, the specimen should be treated with 80% alcohol to restore color.

22. Mounting Specimens are trimmed to desired size and shape so that they fit in the jar. All unwanted and non representative tissues are removed after careful dissection. If the specimen do not remain in natural position after removal of cotton wool packing, fill the cavities with arsenious acid- gelatin. Regular cuts given keeping in anatomical position.

23. Friable specimens can be covered by thin layer of arsenious acid gelatin. Bile stained specimen are soaked in solution of calcium chloride for 24 hours to avoid discoloration of mounting fluid.

24. Mounting procedure Museum jars and boxes Center plates Stitching specimens to center plate Fixing the center plate Filling and sealing

25. Factors affecting fixation Buffering Penetration Volume Temperature Concentration Time interval Position of the tissue

26. Special methods Maceration - Used to demonstrate bony lesions eg ; osteogenic sarcomas, osteomas and tuberculosis. Calculi - Calculi are cut in half with fine fretsaw and cut surface is polished with sand paper. - Dry mounting in closed jars. Amyloid - Iodine technique - Congo red technique

27. Presentation Museum specimen should be clearly labelled and a system of cataloging should be employed which allows easy and rapid access.

28. Labelling Rectangle of Perspex sheet 1/16 th of an inch in thickness which is cemented in the center at the bottom of the outside of the box or the bottom of the center plate.

29. References MUSEUM TECHNIQUES: A REVIEW BY R. J. V. PULVERTAFT From the Westminster Hospital School of Medicine, London

30. Thank you….